The invention relates to an internal combustion engine with at least two camshafts arranged beside each other in the cylinder head, and it is especially applicable to internal combustion engines with an intake camshaft and an exhaust camshaft.
This type of internal combustion engine is already known from EP 0 945 598 A2. In a special model of this internal combustion engine, the ends of both camshafts, which are each supported in a journal bearing in the cylinder head of the internal combustion engine, are each connected to a mechanism for varying the control timing of the engine""s gas exchange valves, each including a drive unit connected through a drive means with the crankshaft of the engine and of an output unit connected to the respective camshafts. Between the drive unit and the output unit of each mechanism, at least two hydraulic compression chambers are constructed in the usual manner, which act in opposition to each other and which can be alternately or simultaneously charged with a pressure medium, thus causing a relative rotation or a hydraulic clamping of the respective camshaft to the crankshaft of the engine. In this way, the feeding and discharge of the hydraulic pressure medium to and from the compression chambers of both mechanisms are each regulated separately by an electromagnetic control valve which is fluidly connected with the compression chambers through the journal bearing of the respective camshaft as well as through pressure medium channels in the camshaft and in the cylinder head of the engine. Each of these electromagnetic control valves consists normally of an electromagnet with an electrical socket on the front and a cartridge which is connected to the electromagnet and which can be inserted into a drilled hole designed as a valve holder in keeping with the usual solution. This hole is incorporated into the cylinder head walls of the engine in the region of the journal bearing of the camshaft running parallel to it, and extends transverse to the crankcase of the engine in order to save space for the positioning of the control valve.
The disadvantage of this familiar engine design is, however, that the electromagnetic control valves for the mechanism for varying the valve control times, in spite of their transverse positioning alongside the cylinder head walls, require an enlarged clearance for the engine in the vehicle, which is not available in every case or can only be accomplished through costly restructuring of the whole engine design.
Moreover, the electromagnets of the control valves and their electrical sockets are exposed to an increased danger of contamination by their unprotected positioning on the engine. In the long term, this can lead to malfunctions or to failure of the electromagnetic control valves and therefore also to failure of the mechanisms for varying the valve control reaction times of the engine.
The object of the invention is to design an internal combustion engine with at least two camshafts arranged alongside each other in the cylinder head, in particular with an intake camshaft and an exhaust camshaft. This engine only requires a minimum clearance in the vehicle because of a space-saving arrangement of the electromagnetic control valves for the mechanism for varying the valve control reaction times and is distinguished by simple measures for the greatest possible avoidance of failure of the electromagnetic control valves due to contamination.
In accordance with the invention, this object is fulfilled in an internal combustion engine by designing the valve holders of the control valves as separate flanged connectors with a plunge-cut hole. These are attached directly above the journal bearings of the camshafts on the cylinder head of the engine in such a way that the control valves are arranged with their cartridges facing away from each other and with their electromagnets arranged side by side, directly facing each other on a common longitudinal axis running transverse to the longitudinal axis of the camshafts. The electrical sockets of the electromagnets are each arranged parallel to the front side on an extension, facing away from each other, alongside the electromagnets and parallel to the longitudinal axis of the control valves.
In a further embodiment of an internal combustion engine built according to this invention, the valve holders of the control valves preferably feature a trapezoid-shaped cross sectional profile and are bolted together by the larger of their two parallel surfaces on the level facing surface of a cylinder head cover, which can preferably be mounted on the engine""s cylinder head. For this purpose, several additional clamping collars for bolts are molded onto the larger parallel surfaces of the valve holders, which can be screwed into corresponding threaded holes in the facing surface of the cylinder head cover. A trapezoid-shaped cross sectional profile of the valve holders has proven to be the most advantageous for saving both space and weight. It can also be replaced, however, by another suitable cross sectional profile, for example, by a half round or a rectangular cross sectional profile.
Another significant characteristic of the internal combustion engine constructed in accordance with this invention is that a bearing half of the journal bearings in the camshafts, constructed in the familiar fashion of at most two parts, is integrated into each cylinder head cover and is connected through pressure medium conduits incorporated in the cylinder head cover as well as in the valve holders with the plunge-cut holes in each of the valve holders situated above the journal bearing. Starting from the plunge-cut holes for the control valves in the valve holders, the feeding and discharge of the hydraulic pressure medium to and from the compression chambers of the mechanism for varying the valve control times takes place through these pressure medium conduits as well as through the journal bearings of the camshafts and through the pressure medium channels located in the camshafts. As a result, the pressure medium conduits incorporated into the valve holders and the cylinder head covers are each formed primarily by two of the plunge-cut holes in the respective valve holders which proceed perpendicularly through the cylinder head cover and meet inside of the journal bearing of the camshafts in corresponding ring canals on the ends of the camshafts. These ring canals are connected to the pressure medium canals in the camshafts. A design of this type, however, with the described arrangement and construction of the control valves and their valve holders, should not be limited only to internal combustion engines having journal bearings for the camshafts integrated in the cylinder head cover. It is also feasible, by analogy, for use with small adjustments, for internal combustion engines with camshaft journal bearings situated separately from the cylinder head cover. It is also conceivable to construct the control valves, which can be inserted into the valve holders and are preferably bolted to them, in one piece with the valve holders by utilizing an inseparable connection.
With regard to the electrical sockets protruding from the front sides of the control valves"" electromagnets which directly face each other in the assembly position, these electrical sockets are situated, due to space requirements, above an extension on a longitudinal axis beside the electromagnets or in a horizontal plane between the electromagnets and the mechanisms for varying the valve control times, and are therefore difficult to access. It is recommended, in the design of an internal combustion engine constructed in accordance with this invention, that these sockets be arranged in such a way that the clearance from the surface of the electromagnets makes it possible to use these surfaces as bearing surfaces during the installation of the cable plug. This means that the clearance of the sockets from the surfaces of the electromagnets corresponds roughly to the thickness of the casing of the cable plug, so that it is possible during manual assembly of the cable plug to establish a secure plug connection between the cable plug and the electrical socket of the electromagnets, without being able to see it directly, by drawing the cable plug up onto the surfaces of the electromagnets and then pushing the cable plug in a straight line along the surfaces.
Furthermore, it is also recommended for the construction of an internal combustion engine in accordance with this invention, that the mechanisms for varying the valve control timing, along with their drive means as well as the valve holders and the control valve electromagnets, including their electrical sockets, be provided with additional protection from contamination by a plastic casing. The cross sectional shape of this plastic casing results primarily from conforming to the contour of the longitudinal section through the end of the engine""s cylinder head with the mechanism along the longitudinal axis of the camshaft, and is preferably secured by a plug-and-socket connection on the engine""s cylinder head. It is also possible, however, instead of using plastic, to use a casing made of a light metal or another suitable material which can also be secured by a bolted connection or something similar on the engine""s cylinder head.
An internal combustion engine, constructed in accordance with this invention, that has at least two camshafts located beside each other in the cylinder head, particularly with an intake camshaft and an exhaust camshaft, therefore features an advantage over the known state-of-the-art internal combustion engines, in that it is no longer necessary to make alterations for the clearance of the engine or to restructure nearby elements of the engine. This is because of the space-saving arrangement of the electromagnetic control valves for the mechanism for varying the valve control timing. The arrangement of the electromagnetic control valves in separate valve holders constructed as flanged connectors on the cylinder head of the engine also has the advantage of making it easy to access them when servicing the engine and making it very simple to clean or replace them. Moreover, by the additional encasement in plastic of the mechanisms, the valve holders and the electromagnets of the control valves including their sockets, a simple measure is taken for preventing contamination-related failures of both the electromagnetic control valves and the mechanisms for varying the valve control reaction times.